DE10336328A1 - Device for processing a silicon substrate comprises evacuating stations, a silicon deep etching chamber, a plasma chamber and a chlorine trifluoride etching chamber - Google Patents

Abstract

Device for processing a silicon substrate comprises evacuating stations (12, 30) for introducing and removing silicon substrates (14), a silicon deep etching chamber (16) for etching a micromechanical structure from the substrates, a plasma chamber (18) as oxide and Teflon etching chamber or as Teflon deposition chamber, and a chlorine trifluoride etching chamber (20) as a further silicon etching chamber with an evacuating handling station (32) for the substrates. The components of the device together form a multiple chamber arrangement which can be extended by further integrated or coupled stations.

Description

The invention relates to a device for processing a silicon substrate according to the preamble of claim 1. For this purpose, from the DE 198 47 455 A a method for etching a silicon layer body is known which has a first silicon layer which is provided with an etching masking for defining lateral recesses, wherein in a first etching process with a plasma is used and in the region of the recesses of the etching masking by anisotropic etching trench trenches are generated. In a second etching process, a separating layer of silicon oxide (SiO ₂ ) lying between the first silicon layer and a further silicon layer is then etched through before the etching of the further silicon layer takes place in a third etching process, a gas phase etching process. The apparatus used for the aforementioned method is not described in detail in the document, but with respect to the required for the first etching process apparatus and the method of the teaching of DE 42 41 045 A directed. With regard to the etching of the oxide separating layer between the first and the further silicon layer, reference is made to the possibility of using a cluster system with a single handling system for a plurality of plasma etching chambers without specifying the further structure of the etching device.

Of the Invention is based on the object, a device for processing specify a silicon substrate in several process stations, which with regard to the production process, the production costs and the quality of the finished product is improved. This includes in particular the saving or acceleration of time-consuming process steps, one possible small footprint of the device in the form of expensive clean room area, which should be minimized, and an improvement in the quality of the product Contamination damage. This is achieved by the characterizing features of the claim 1, which it by the summary of the gas phase etching process important process chambers to make a unit, the advantages mentioned to realize. With regard to the process costs and the duration of the process In particular, the elimination of time-consuming pump-down and smuggling operations intervenes individual process steps noticeable, as they are for separately set up process chambers typical. In terms of the quality improvement the products is the elimination of contamination by the storage of the silicon substrates under vacuum between the important to individual process stations. This applies in particular with regard to further processing after removal of oxide and / or Teflon passivations, wherein the previously exposed substrate surfaces do not re-atmosphere and the exposed to existing contamination or oxidation risk become.

It has proved to be advantageous, in addition to a combination of core devices, to integrate at least one evacuable parking station as a buffer station in the cluster system. This results in advantages in the logistical flow of the processes when the silicon substrates can be stored for certain times under controlled conditions, for example under a vacuum atmosphere. This is advantageous, for example, when individual process steps within the cluster system are particularly fast, for example opening of Teflon or oxide passivations, and if this is followed by a longer process step, for example the etching of a silicon sacrificial layer in a chlorotrifluoride atmosphere. The substrates which have been freed from the thin oxide or Teflon passivation at high speed can advantageously be distributed to a plurality of chlorine trifluoride etching chambers of the cluster plant if they are previously parked in a parking station and fed from there to the individual ClF ₃ process stations. Afterwards, they can be collected again from a number of ClF ₃ process stations in a parking station before further processing if required. Such buffers allow for high process flexibility in the cluster plant, as the distribution of rapidly moving wafers to multiple chambers with slower steps and the subsequent regrouping of the substrates from a plurality of "slower" process chambers to a single batch in a simple manner This bundling is preferably carried out in cassettes, which are advantageously used in particular when entering and / or discharging from the cluster system and in the parking stations.

Farther it has to be useful proven, if at least the handling station and / or the parking station (s) Means for detecting temperature and / or means for heating or cooling the silicon substrates exhibit the substrates between different process chambers to a desired To bring temperature. For heating the substrates are preferably used Radiant heaters or contact heaters. A cooling of Substrates is possible by the supply of refrigerant, for example in the form of helium, to the back of the substrates in the Substrate holders. As means for detecting the substrate temperature are preferably bolometers, thermo-optic radiation meters or touching thermometers uses.

Plasma or ozone stripping chambers can also be used to speed up the process be coupled to the cluster system. These serve, for example, for removing photoresist masks or Teflon-like sidewall passivation layers within the cluster system, wherein preferably an O ₂ plasma stripper or an ozone module is used.

The Overall control of the cluster system is done by a computer control, preferably by a programmable logic controller, by means of a software that allows both the replacement of silicon substrates between the individual process stations through the evacuable handling station as well as the sequence of processes within the individual stations controls.

Further Details and advantageous developments of the invention result from the dependent claims and the description of the embodiments the invention.

The Drawing shows a schematic diagram of the device according to the invention for processing a silicon substrate in several process stations.

To the core elements of a cluster plant 10 First counts an entry station 12 for insertion in cassettes 42 held silicon substrates 14 in the plant. To this infeed station 12 closes, viewed counterclockwise, a silicon Tiefenätzkammer 16 (DRIE Etching Chamber, Deep Reactive Ion Etching), for etching a structure, preferably a micromechanical structure, from the silicon substrate 14 at. The next chamber is a plasma etch chamber 18 which is operable with a selectable substrate bias and can be used for both oxide etching and Teflon deposition or Teflon etching. In the present case, however, an additional plasma deposition chamber is used to deposit Teflon 20 intended. As in the as a cluster plant 10 designated plant group of process stations for processing a silicon wafer substrate 14 at least one etching step takes place in a chlorotrifluoride (ClF ₃ ) atmosphere, joins the chamber 20 at least one additional silicon etch chamber 22 which works with a ClF ₃ -containing process gas.

Further, but not to the core elements of the cluster plant 10 belonging chambers are at least one strip chamber 24 , an additional chamber 26 as needed and at least one parking station 28 , The strip chamber 24 serves to remove organic layers such as photoresist masks.

The parking station 28 takes the silicon substrates 14 as well as the infeed station 12 in larger numbers in cassettes 42 on. Such parking stations 28 can be on demand at different locations in the cluster plant 10 be inserted. The discharge station 30 also collects the individual silicon substrates in cassettes 42 for further transport. The infeed station 12 and the discharge station 30 are shown in the drawing as separate stations, but they can also be combined into a single station. The feeding of the individual stations takes place via a central, evacuable handling station 32 , which is also shown only schematically in the drawing with a drive 34 , a joint 36 and a substrate carrier 38 ,

In the drawing are still at the parking station 28 and the handling station 32 devices 40 for temperature detection and / or for heating the silicon substrates 14 shown. Such devices can also be provided in other chambers as needed. The at the infeed station 12 , the parking station 28 and the discharge station 30 illustrated cassettes 42 serve to accommodate predetermined lot sizes of silicon substrates 14 , for example, of 25 substrates in a wafer cassette 42 , The individual stations are coupled to separate or common devices for evacuation, which are shown for clarity in the drawing as little as, for example, feeders for the process gases, valves, mass flow controller and the like. As is the central handling station 32 Having means for generating and monitoring a vacuum, the entire process after the introduction of the substrates 14 and evacuating the Einschleus- or Russchleus stations without further pumping and venting times before the successive individual stations run, the evacuated handling station 32 the replacement of the substrates 14 between the stations.

A possible construction of the device according to the invention will first be explained using the example of an etching process with photoresist mask technique and Teflon passivation of the structures in the silicon substrates. Here are already masked substrates 14 after their introduction via the cassette station 12 one or even several parallel silicon DRIE (Deep Reactive Ion Etching) Etzkammern 16 supplied, where structures, preferably micromechanical structures are etched into the silicon substrates. Such methods are for example in the DE 42 41 045 A or DE 198 47 455 A1 described.

To the DRIE etch chamber 16 close one or more plasma etching chambers 18 with be preferably high ion density and selectable substrate bias voltage, which are embodied, for example, as ICP (Inductively Coupled Plasma), MORI (Magnetically ORiented Inductive) or ECR (Electron Cyclodron Resonance) plasma etching chamber and for removing the soil oxide in the micromechanical layer structure of the silicon substrate 14 serve. This bottom oxide is present in the structure of the silicon substrate as a separating layer between two silicon layers in a known manner. The chamber 18 also has means not shown in the drawing for the supply and flow control of the required oxide etching gases such as fluorocarbons and supply means for CO, oxygen, nitrogen and noble gases. The etching process in the chamber 18 At the same time, using fluorocarbons results in the sidewalls of the silicon trench structures being cleaned, deoxidized, chemically activated, and covered with a thin layer of fluorocarbon, which results in the adhesion and impermeability of the subsequent deposition in the plasma deposition chamber 20 Teflon-deposited Teflon layers on the sidewalls of the etched structures improved.

The deposition chamber 20 for Teflon deposition is also formed as a plasma chamber with high ion density of over 1011 ions per cc, for example as ICP, MORI, or PIE (Propagation Ion Etching) plasma source. In this chamber 20 the substrate surface is covered with a closed Teflon-like film. To produce the Teflon layer, gaseous Teflon precursors such as C ₄ F ₈ , C ₃ F ₆ or C ₄ F _{6 are introduced} into the chamber. The plasma deposition chamber 20 is operated at low process pressure, for example, 1 Pa, with particularly uniform layers with high reliability for the Teflon passivation are deposited.

After Teflon separation in the chamber 20 a Teflon etching, which takes place in the plasma etching chamber 18 or another, not shown, similar chamber is executed. Here, the on the bottom of the structures in the silicon substrate 14 Controlled Teflon precipitate controlled remotely controlled, wherein on the sidewalls of the trenches resulting Teflon protective films are not attacked appreciably. As Teflon etching gases CF ₄ , C ₂ F ₆ , SF ₆ or argon, neon, O ₂ , O _{3 are} fed controlled, wherein the process pressure is maintained by about 1 Pa. The deposition chamber 20 and the etching chamber 18 may also be implemented as a single chamber, wherein the composition of the process gases, the process pressure, the plasma power, and the substrate bias determine whether to be deposited or etched.

The next step is in a ClF ₃ chamber 22 the etching of a silicon sacrificial layer, which is below that in the etching chamber 16 fabricated structures in the silicon substrate 14 wherein cantilevered micromechanical structures can be produced, as shown in FIG DE 198 47 455 A is described. The chamber 22 not shown means for supplying and flow control of a process gas containing ClF ₃ , means for monitoring and adjusting the process pressure and means for extracting the process gases and reaction products. Furthermore, the chamber 22 Have means for heating or heating or for cooling the silicon substrates, for example, to evaporate absorbed moisture on the surface, residues of Teflon or residues of ClF ₃ and reaction products from the substrate surface after the process. During the process between about -40 ° C and 0 ° C, preferably kept at -25 ° C, so the wafer is cooled.

After ClF ₃ etching of the sacrificial layer in the silicon substrate 14 the core process in the processing of the silicon substrates is completed and the substrates could in principle in this state the cluster plant 10 over the discharge station 30 leave. In the device shown in the figure, however, in addition a stripping chamber 24 and a parking station 28 arranged before the substrates 14 over the discharge station 30 the cluster plant 10 leave. In this embodiment are still in the cluster system 10 even a non-illustrated, applied before the start of process photoresist mask and the teflon deposited in the structure trenches sidewall passivation layers removed again. The strip chamber 24 can be carried out as an O ₂ plasma stripper or as an ozone strip module. In this chamber 24 All organic layers are removed from the wafer surface.

The parking stations 28 can be inserted anywhere between the process stations in the cluster system at a suitable location, especially where fast and slow process steps follow each other, so that an intermediate storage or the removal from a cassette supply are expedient. In the illustrated embodiment, the silicon substrates 14 to the discharge station 30 spent in cassettes 42 arranged and leave from there the cluster plant 10 ,

In the embodiment, further devices 40 for temperature detection and for heating the parking station 28 and the central handling station 32 assigned, so that the temperature monitoring and any required heating is assigned to these stations. If required, however, corresponding devices can also be assigned to other stations.

A slightly different process flow and so on with a modified arrangement or use of the different parts of the cluster plant 10 arise when, for example, due to increased process temperatures, a photoresist mask technique can not be used and is replaced by a hardmask technique with, for example, an oxide masking and oxide passivation of the silicon structures. In this case, the DRIE etch chamber 16 an oxide etching chamber corresponding to the plasma etching chamber 18 for structuring an oxide mask and a process chamber for removing the photoresist layer corresponding to the stripping chamber 24 upstream. In these process steps, the underlying oxide is first etched away in the openings of the photoresist mask, and thus the photoresist mask is transferred into the oxide layer with high precision, for example in an oxygen plasma or ozone stripping station 24 the photoresist mask is removed. Alternatively, however, it is also possible to use the silicon substrates 14 only in this pretreated state in the cluster plant 10 to bring in, that is to carry out the oxide masking in advance outside of the cluster.

in the Following the creation of the oxide mask correspond to the process steps and the process chambers used first those of the previously described Process with a photoresist mask and a passivation by a teflon layer.

The silicon substrates 14 So be in the DRIE etching chamber 16 spent for etching the desired structure into the silicon wafer substrate 14 wherein the oxide mask in the etching chamber 16 is removed only to a very small extent, since the selectivity of this process is very high and the silicon oxide is removed in contrast to silicon only to a very limited extent, typically about in the ratio 1: 300.

The etching of the structure in an upper silicon layer of the substrate 14 Then, due to the high selectivity of the DRIE etching process, it ends practically also at the oxide separating layer present in the substrate between the upper silicon layer and the silicon sacrificial layer below the oxidic separating layer.

The substrates 14 are then in the plasma etching chamber for the next processing step 18 spent to remove the oxide separating layer between the two silicon layers, as already explained in the above-described process.

Following the etching chamber 18 become the silicon substrates 14 when using an oxide masking and Oxidpassivierung then first in a stripping chamber 24 spent removing all Teflon-like films formed on the surface of the substrate in the pre-processes of the DRIE or oxide etching. For this purpose, an oxygen plasma or an ozone effect on the substrate surface is used. At the same time, the silicon surfaces of the substrate become 14 Oxidized, so that ideal conditions for the subsequent application of oxide films for passivation of the sidewalls of the structure trenches in the substrate 14 ,

Instead of Teflon deposition in the previously described process, passivation now occurs through an oxide layer, which is also located in the plasma deposition chamber 20 can be performed to produce a closed, thin silicon oxide film on the surface of the substrate 14 , To produce the silicon oxide film, silicon carrier gases such as, for example, silanes or TEOS (tetraethylorthosilicate) and an oxide radical carrier such as, for example, O ₂ , O ₃ , NO, N ₂ O or CO _{2, are introduced} into the chamber. So it's in the same chamber 20 the choice of the gases supplied determines which layers are actually deposited. In the case of oxide deposition, however, the plasma deposition chamber may 20 also removed from the core cluster structure and executed, for example, as an LTO (Low Temperature Oxide) batch deposition system. A batch plant outside the cluster has the advantage that in this oxide deposition process a variety of substrates 14 can be coated at the same time. On the other hand, often chosen for the process of oxide deposition chamber shapes such as tubular chambers, which are structurally difficult only in the cluster system 10 can be integrated directly.

After oxide deposition, the substrates migrate 14 in an oxide etching chamber, for example, in the plasma etching chamber 18 , wherein as the process gases for the etching suitable gases such as CF ₄ , C ₃ F ₈ , C ₄ F ₈ , C ₃ F ₆ or C ₄ F _{6 are} supplied. In this step, the previously applied oxide passivation is controlled again removed from the bottom of the structure trenches, without the side wall protection films of the trenches are significantly attacked. The oxide step can even be used to grow an additional Teflon protection film on the sidewalls parallel to the Bodenoxidätzung so that there is a particularly reliable passivation of oxide and above Teflon is generated. This layer combination is particularly dense and pinholefrei, since it is a double layer, which can be obtained without additional effort by appropriate choice of process gases.

The further process steps of the process with an oxide passivation correspond in turn those with a Teflon passivation. The substrates are thus again in succession in a ClF ₃ etching chamber 22 for sacrificial silicon etch etch and finally via the central, evacuable handling station 32 , optionally with the interposition of a parking station 28 , to the discharge station 30 spent. These steps and the required chamber construction have already been described with reference to the process of Teflon passivation and need not be discussed again here.

Next to separate stations 12 . 30 or a combined station for feeding and discharging the silicon substrates 14 belong to the core of the cluster plant 10 So at least one operable with a substrate bias plasma chamber 18 as oxide or Teflonätzkammer or Teflonabscheidekammer, at least one ClF ₃ etching chamber as a further silicon etching chamber and preferably at least one silicon Tiefenätzkammer, for example in the form of a DRIE etching chamber 16 for anisotropic etching of a structure from the silicon substrate 14 , as well as an evacuable handling station 32 for the silicon substrates 14 , Other process stations, such as the creation of a patterned oxide mask, can be sent to the cluster facility 10 be coupled, for example, if the temporal sequence of the process steps is thereby improved.

Claims (9)

Apparatus for processing a silicon substrate in a plurality of process stations, wherein at least one etching step takes place in a chlorotrifluoride (ClF ₃ ) atmosphere, characterized in that at least one evacuable station ( 12 . 30 ) for introducing and / or discharging the silicon substrates ( 14 ), at least one silicon deep etch chamber (DRIE etch chamber, 16 ), for etching a structure, preferably a micromechanical structure, from the silicon substrate ( 14 ), at least one plasma chamber operable with a substrate bias voltage ( 18 ) as an oxide or Teflon etching chamber or as a Teflon deposition chamber and at least one Chlortrifluorid etching chamber ( 20 ) as a further silicon etching chamber with an evacuable handling station ( 32 ) for the silicon substrates ( 14 ) to a cluster plant (multi-chamber plant, 10 ), which can be connected as required by further integratable or connectable stations ( 20 . 24 . 26 . 28 ) is expandable. Device according to claim 1, characterized in that the plasma chamber ( 18 ) can be used in the same step simultaneously on the one hand as Oxidätzkammer and on the other hand as Teflonabscheidekammer and as Teflon etching. Apparatus according to claim 1 or 2, characterized in that at least one evacuated parking station ( 28 ) as a buffer station in the cluster plant ( 10 ) is integrated. Device according to one of the preceding claims, characterized in that at least the handling station ( 32 ) and / or the parking station ( 28 ) Means for temperature detection ( 40 , T) and / or means for heating or cooling ( 40 , H) of the silicon substrates ( 14 ) having. Device according to one of the preceding claims, characterized in that the Chlortrifluorid etching chamber ( 20 ) Means for temperature detection ( 46 , T) during wafer processing. Device according to one of the preceding claims, characterized in that the Chlortrifluorid etching chamber ( 20 ) Means for cooling ( 46 , K) the Substate ( 14 ) during wafer processing. Apparatus according to claim 5 or 6, characterized that the temperature of the substrates during wafer processing between -40 ° C and 0 ° C, preferably is kept at about -25 ° C. Device according to one of the preceding claims, characterized in that a plasma or ozone strip chamber ( 24 ) to the cluster plant ( 10 ) can be coupled. Device according to one of the preceding claims, characterized in that the silicon substrates ( 14 ) when entering and / or discharging from the cluster plant ( 10 ) in cassettes ( 42 ) are held.